It's taken more than two seasons, but the delicate dance between Cesare and Lucrezia Borgia finally ended with more than flirtation in Season 3's third episode, the appropriately titled "Siblings."

"I think she is to blame, right?" joked Francois Arnaud, who plays Cesare. "Because she makes the first move, right? She just couldn't resist me anymore."

After fighting with Alfonso (Sebastian De Souza) at their wedding reception, Lucrezia (Holliday Grainger) crawled into bed with Cesare, who was shocked but didn't exactly protest his sister's boldness.

"Only a Borgia it seems, can truly love a Borgia," Lucrezia said. "Why deny yourself a pleasure for which we're already accused?"

With her reputation already slandered by rumors that the two are lovers, Lucrezia seeks comfort in the arms of her only safe harbor. Cesare and Lucrezia, long pawns for the machinations of their father, Pope Alexander VI (Jeremy Irons), are beset with new problems that once again push them to seek each other out.

For Arnaud, the sibling sex was a natural progression for the characters, who can't even trust their father.

"It felt like it was meant to happen. Of course they do have sexual feelings for one another, but it mostly comes from a deep, deep love," he said. "I think they also both tried to have romantic relationships with other people and it hasn't worked--and probably because they keep comparing everyone who comes into their lives to that ideal of brother or sister that they have."

Arnaud, who said he doesn't has to agree with what a character does in order to play him, talked more about the mixed emotions Cesare feels after making love to his sister, and the balance the actors and creator Neil Jordan had to strike with the incest storyline.

It finally happens: Cesare and Lucrezia get together.Yeah. Together. [Laughs.]

Tell me about the conversations that you, Neil and Holliday had about those scenes.It was funny because I remember when we first got there three years ago. When we first got to Budapest, my first rehearsal was with Holly. It was for our very first scene together. We were lying in the garden and Neil kept insisting that we had too many innuendos or it was too romantic or too sexual. And we both argued that it was already all over his writing.

It was like there was nothing else to do. So we kept asking, "Do you want us to play against it?" Instinctively that's what came to us, and that's what worked. We had arguments, really big discussions about it in the first year, and he said, "Well, we don't know if that happened. It could all be rumors."

After two and a half years of teasing everybody [laughs], here we are. It's a TV series; we can't keep going like this forever. The curtain has to fall.

Did Neil say anything this season about like, "Hey, we're finally gonna do this?"Yeah, he was like "Go for it. Everything I told you not to do, do it now." [Laughs.]

I guess what I'm getting at is did you talk about the delicacy of it, and how viewers might react to incest. You know, "Don't look like you're just jumping bones."There are so many emotions involved in that sexual act that it couldn't have been just jumping each other's bones. [Laughs.] There's a lot more involved and it's a lot of mixed emotions. When it happens there's pain, there's relief, there's the feeling that it was inevitable. There's also fear for the future and it all happens at once. And that's what love can be.

Did you talk about how you would play those scenes specifically?Well, yes and no. We had so many versions of that script actually because they kept rewriting it. They were never happy with it. It was always too early or too late. ... They played around with it a lot before finding the right balance of what felt right after three years of [the characters] desperately wanting each other.

Cesare seems unhappy afterward. It seems like he really regrets it.Oh, yeah. It's definitely eating him. There are different kinds of love and when you love someone as much as Cesare loves Lucrezia, you want to possess her but you wish her happiness more than yours. And I think Cesare has many doubts about what's better for her.

I'm sure, for himself, he enjoyed the whole thing. [Laughs.] I don't think he has many personal regrets about it. But I think for her especially he feels like he should be the bigger man. He should lead her the right way. And he probably feels that he failed her in a way.

Will this be a problem for them throughout the season? Well it haunt him?I can say that it's a major theme of the whole season to the very end. They have a very kind of Lady Macbeth relationship toward the end of the season.

What would you say to those viewers who might stop watching because incest is not best?Is incest worse than murder? [Laughs.] People can be so prudish. This is so funny actually. It's like the MPAA ratings; I'm always surprised that like if someone walks out of the shower in the nude it can't be seen by 17-year-olds, but then 13-year-olds are allowed to go see people blowing up other people's heads for three hours. Amazing. I don't know what people are so afraid of.